Wheelchairs have been in use in our mobile society for more than a century. Wheelchairs are typically used by elderly and disabled people, or by people recovering from surgery, injury or illness. However, wheelchairs typically fall short of providing desired mobility to their users in a number of aspects. First, wheelchairs are typically designed for smooth surfaces, such as hospital floors and concrete sidewalks. The wheels are generally thin, with solid rubber tires. A ring is placed on the outside of each of the rear wheels, providing a gripping surface for those riders who are able to propel themselves by pushing forward on the rings and thus turning the wheels. While this arrangement works fine for short distances over smooth surfaces, prolonged use by the seated rider can damage the soft tissue in the rider's shoulders, thus rendering the rider less mobile over time. Furthermore, the design of the thin, solid rubber tire makes it difficult to propel such a chair over uneven surfaces, such as sidewalks, curbs, and the like, and accommodations must be made in the form of ramps to allow a wheelchair to safely pass over them.
The size of typical wheelchairs also suffers shortcomings. The width of a typical hospital-style wheelchair requires larger doorways, and the weight of such a chair makes it difficult to load such a chair in an automobile, and often involves costly modifications to an automobile to swing the chair around from the side of an automobile to a stored position behind the automobile.
Modified wheelchairs have been developed in recent decades to provide a smaller, lighter wheelchair. Wheelchair racing is now a competitive sport around the world. Inflated tires have been used to provide some sort of shock absorption and safer operation over uneven surfaces and at higher speeds. However, with these improvements comes the desire for wheelchair riders to go farther and faster, thus increasing the magnitude of shock delivered to the seated rider, and more difficulty traversing uneven surfaces. In such cases, additional injury can be sustained to the rider's spine, as inflated tires do not provide sufficient shock absorption to protect the rider in many cases. For example, while some riders can take their wheelchair directly over a curb without a ramp, this can damage the spine of the rider, especially over a large number of instances. Self-propulsion of these wheelchairs still results in soft tissue injury to the rider's shoulders.
Electric wheelchairs eliminate the shoulder injury, but suffer their own shortcomings. Electric wheelchairs are heavy, expensive, and more difficult to load into and out of an automobile than conventional wheelchairs. More importantly, an electric wheelchair can leave a rider stranded if the battery is drained or there is some sort of failure in the drive train. These chairs are also unsuited for uneven surfaces, so the mobility of the rider is limited even by the best electric wheelchairs. Thus, there is a heartfelt need for an improved wheelchair design that increases the rider's mobility, protects the rider from shoulder injury, and also protects the rider from shocks delivered from impact to the wheels over uneven surfaces.